Truck-mounted apparatus or similar vehicles for the emplacement of concrete, for example a pumper for concrete mixed in transit, generally include a plurality of carrier arms which are hingedly joined and/or similarly connected, linked or coupled to one another. The arms can be moved or swung with respect to one another. Such apparatus, furthermore, can include a concrete pump and conduits extending along the arms to convey the concrete. The apparatus allows folding of the arms into a more compact or rolled-up condition as a rest position and unfolding into an operating condition or position.
The concrete distributing conduit system is additionally connected to a rotary turntable or tower. Apart from such vehicular concrete pumpers, such apparatus can be employed in combination with a tower crane to emplace concrete in the construction of high rise and similar tall structures. They are also used individually as so-called stationary concrete-distributing apparatus.
The primary use of such apparatus is for delivering concrete in flowable form within the effective reach thereof, i.e. the effective distance from the vehicle or tower to the location to which the concrete is pumped. Of course, the greater the reach of the apparatus, the more favorable is the operating range and the longer the vehicle can remain at one location before being relocated to serve other locations which could initially not be covered.
Accordingly, a foremost aim in the development of such apparatus has been the increase of the effective or operational reach, or longitudinal range thereof. However, there are limits due to bulk, weight and balance.
It has been suggested to extend the reach of the entire concrete distribution apparatus by bolting at the terminal carrier arm an additional boom or extension-arm piece or element, for example by screw threads. It is also known to furnish this extension arm as a telescopically extensible element.
A further proposal to extend the effective reach of apparatus for handling concrete in fluid form contemplates the provision of additional extension-arm piece or boom element which is swung to be laterally disposed along the terminal carrier arm in the rest condition and which is swung forwardly and secured by lock pins or similar means.
These prior art arrangements generally requires extra effort, either effort by operating personnel or extra technical effort to move the additional carrier arm from the corresponding rest position into the respective and proper operating position, and vice versa.